Frangible materials are materials, such as glass, that tend to break up into fragments when subjected to a deforming force or impact, as compared with non-frangible materials that elastically deform and retain cohesion when subjected to comparable deforming forces. The phrase “glass material” refers to any of various amorphous frangible materials formed from a melt by cooling to rigidity without crystallization. The most commonly known glass materials are usually transparent or translucent material consisting typically of a mixture of silicates, but the phrase “glass material” is not limited to silicate-based glass unless otherwise specified.
Frangible structures (i.e., structures formed using one or more frangible materials) are utilized in a wide range of practical applications ranging from small and simple to large and complex. Most frangible structures are designed to undergo structural failure (break away) when struck by an externally applied impact force. For example, light poles or airport lighting structures are designed to break away when hit by a vehicle or plane in order to lessen damage to the vehicle/plane and minimize injury to the passengers. Some frangible structures are designed to undergo structural failure in response to an externally generated command signal. For example, transient electronic devices are frangible structures that include one or more electronic devices (e.g., integrated circuit (IC) chip and/or printed electronic devices) mounted on a stress-engineered glass substrate along with a trigger mechanism. The glass material forming the glass substrate is stress-engineered (e.g., intentionally fabricated using thermally tempered, ion-exchange treated, or lamination techniques) to store potential energy in the form of residual internal stress gradients such that, when the stress-engineered glass substrate is subjected to a relatively small initial fracture force generated by the trigger mechanism, the stored potential energy is released in the form of a propagating fracture force that is quickly transferred throughout the glass substrate.
Currently, there are no known methodologies for producing complex frangible structures that undergo on-command structural failure in response to a single initiating force (i.e., where the single initiating force has an trigger area much smaller than the overall structural area, preferably smaller than 1 μm2). That is, there is no practical way to generate a large complex structure, such as an airplane wing section, from a single (integrally-molded or machined) piece of frangible material. Conversely, when multiple discrete stress-engineered glass structures are adhered together to form the complex shape, propagating fracture forces are unable to transfer from one frangible glass structure to an adjacent frangible glass structure, thereby requiring multiple triggering forces (i.e. one trigger mechanism for each frangible glass structure) to achieve complete structural failure of the entire complex frangible structure.
What is needed is a methodology for generating complex stress-engineered frangible structures that reliably undergoes on-command structural failure in response to a single triggering force with a triggering area much smaller than the structural area.